We propose a new technique for investigating photopigment kinetics. This technique involves color matching, a non-invasive psychophysical task. By examining the dependence of a color match on retinal illuminance it may be possible to develop a sensitive index of the state of the outer retina. Color matching, a widely used clinical technique, for instance in the Nagel anomaloscope, depends on the density of the cone photopigments. At a given level of retinal illuminance, photopigment density is maintained by a dynamic balance between the processes of photopigment bleaching (due to the absorption of light) and photopigment regeneration (via a series of biochemical reactions). Illuminance dependent changes in the color matches of normals will be compared with those of patients with known retinal pathology. Specific predictions made by theories concerning color matching will be tested on normal subjects. This will provide information on the soundness of the underlying theory. Patients will be selected on the basis of those most likely to show photopigment kinetic abnormalities. Specifically we will look at patients who have known disorders of the RPE-photoreceptor interface (patients recovering from retinal detachments), and diseases in which kinetic factors have previously been implicated (retinitis pigmentosa). Patients with less common disorders, such as some of the night blinding disorders, will be tested if possible. Data obtained in this study will allow us to evaluate the proposed technique as a research and as a clinical tool.